Oracle database customers running version 11g Release 1 have until the end of this month to upgrade, or else face increased annual maintenance fees.

The vendor provides five years of Premier Support after a new product becomes generally available, as 11gR2 did in August 2007. After that, Extended Support is available for another three years, but at extra cost.

There's also a Sustaining Support option available for as long as customers desire to have it, but this offers fewer features, including no new patches, bug fixes, and regulatory updates.

Customers who already moved to 11gR2 still have Premier Support until January 2015.

It's not clear how many Oracle database customers the end of Premier Support for 11gR1 will affect, although the number could be substantial, given Oracle's large share of the overall market.

"I think it is fair to say that there are many customers who have not yet upgraded, though a minority of the total," said IDC analyst Carl Olofson.

About a quarter of Ottawa, Ontario, remote database administration company Pythian Group's customers have at least one 11gR1 database, while 55 percent have at least one 11gR2 instance, according to figures the company provided on Thursday.

However, many of the Oracle databases being managed by Pythian are versions even lower than 11gR1. "These customers have made a clear decision to allow these environments to fall out of product support, and as a result newer releases' support dates are immaterial to them," said Pythian Group founder and executive chairman Paul Vallée.

"I do not have any idea as to the numbers [of companies remaining on 11gR1]," said John Matelski, president of the Independent Oracle Users Group. "What I can say is that we have seen a trend whereby companies and agencies have been upgrading in a shorter time-frame to Oracle 11g than previous major releases."

"Also, our experience shows that it is typical for companies to wait for the second release of a database to come out when they are upgrading, so many may have bypassed the 11gR1, but will take advantage of 11gR2," added Matelski, who is also CIO for Gwinnett County, Georgia's government.

Gwinnett County is running Oracle database version 10g in production and has 11gR1 running only in test environments, Matelski said. "Our typical methodology for major release upgrades is to stay one release behind, ensuring that all of the bugs have been ironed out."

Pythian Group senior consultant Marc Fielding echoed Matelski's view.

It's not as if new Oracle database releases aren't ready for prime time, Fielding said. "It's just that most of our clients have lengthy testing cycles for these major new releases, and tend to only make it to the final production stage several years after initial general availability."

That said, there are other important reasons some customers delay making database upgrades, according to Fielding. One may be that they simply have a stable, working platform, he said. "If you have an application running very stably, doing an upgrade still involves a fair amount of effort and risk. It could even involve downtime." Budgetary reasons could be another concern, he added.

The big companies Pythian works with, however, probably won't move to 12c production systems that soon, according to Fielding. "I'm not seeing that. I'm seeing it even the almost the other way around, with large enterprise customers are interested in 12c, but they will be testing it in the labs for a number of years."

Customers may also choose to start running existing database workloads in Oracle's public cloud, which is offering database instances on-demand, rather than commit to a traditional on-premises upgrade.